I use ivermectin 3/4 of the time, and something with Prazanquitel (sp?) once. My horse is allergic to Moxidectin, otherwise I'd use it at some point too.You will get conflicting reports. Some say to rotate, others say it's not necessary.

I rotate every worming from Ivermection to Equimax ( I really like this, and so does my vet). The way my vet told me was what one wormer didn't get the other kind would and if you use the same kind all the time the body becomes immuned to it.. Like JustDressageIt said everyone will most likely tell you something different. But the main thing is to go by what works best for your horse. :)

I just went to a seminar that seminole feed was putting on. Sorry starting to run off on a bunny trail, anywho they had a rep there from Pfizer there and she stated that the best treatment is to rotate every 2 months between the 3 classes: Benzimidazoles, Macrocyclic, and Pyrantels.
If you do a daily wormer that you still need to use paste twice a year, what I liked was that she didn't use brand names unless someone asked what brand was in a classes, she didn't push any products.

Actually, all of those recommendations are out-dated and poor. The typical rotational deworming program and paste dewormers are both poor choices due to the development of parasite resistance to commonly used drugs and the fact that controlling parasite reinfection rates can be managed by deworming only 2-4 times a year. Rotational deworming is no longer an adequate or appropriate deworming program for adult horses. This "recipe" is about 40 years old and was designed at a time when a different type of GI parasite was the most prevelant and when different drugs were in use to control parasites. It doesn't take into account the difference in the current situation to the one 40 years ago when large strongyles were the main issue rather than small strongyles which have a very different life cycle. Nor does it take into account that the drugs we use now are all broad spectrum and have different lengths of time when they prevent egg shedding from occuring after dosing. There are also too many issues with strongyles developing resistance to 2 of the 4 most commonly used dewormers on the market---fenbendazole (more than 90% of areas tested have resistant strongyles) and pyrantel (around 1/2 of areas tested have strongyles resistant to this drug). And resistance is starting to be seen in strongyles to ivermectin---1st study showing it was done in KY in the last couple of years.

It's now known that all adult horses living in the same situation do not necessarily need to be dewormed on the same schedule. 50% of horses in a herd will control parasite loads on their own due to natural resistance. Only about 20-30% of horses carry heavy parasite loads. Thus each horse should be dewormed based upon an understanding of his own personal resistance to parasites. The best recommendation is now 2-4 dewormings a year based upon knowing which horses carry lots of parasites and which tend to carry little parasite load.

All adult horses in the continental US/Canada should be dewormed spring and fall with ivermectin/praziquantel or moxidectin/praziquantel. Other than those 2 standard dewormings, the rest of the deworming program should be based upon location and the horse's own resistance to parasites. The new recommendation is 2-4 dewormings per year based upon fecal egg counts used to determine the normal amount of egg shedding each horse does during the time of year when the weather in your area is most conducive to strongyle larva development and environmental survival. In the northern states in the US and in Canada, this means running a fecal egg count in the middle of summer (3 months after spring dosing if you used ivermectin or 4 months after spring dosing if you used ivermectin). In the southern US and Mexico you would be looking at testing in the middle of the winter (same time after spring deworming as listed above). Then based upon the number of eggs per gram of feces you can determine if you need more than the spring/fall dewormings and if so if you need 1 or 2 more dosings.

In the northern US and Canada, deworming should be discontinued during the winter months because the environmental conditions are not conducive to reinfection---that time of year has been proven to have extremely low reinfection rates. In the southern US and Mexico the opposit is true....deworming can be discontinued during the heat of summer because temps over 85 degrees lead to the infective strongyle larva dying quickly in the environment so the reinfection rates are lowest then.

For more detailed information check out the deworming webinar that was aired via The Horse magazine's website in April. Be prepared to sit for a while because it is an hour long presentation, but it's well worth the time. The veterinarian gives you all the information on strongyles and deworming in adult horses that you've always wanted to know and then some. It is a wonderful lecture. (And have plenty of paper and a pen.) http://www.thehorse.com/Video.aspx?vID=1…(Craig R. Reinemeyer, DVM PhD --parasitologist)

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